marking refund

Marking (#62)

Fixed resend of refund in case of non-fatal error (#60)

Added feature to check State of Invoice/Creditmemo before sending to …

…KKM. (#59)

release v2.3.14 (#58)

bump 2.3.12

bump 2.3.11

Move payments source model (#52)

* Move Source model Payment methods to Base module

* Update year in copyrights

hot fix (#51)

fix return value type.
update version.

bump 2.3.8